Power line Communication (PLC) becomes a preferred communication method in communication network of power system since a distribution network has rich user resources and economic efficiency.
However, a power line channel is not an ideal channel. This is because the power line has a low reliability, due to serious noise interference on the power line, changeful load situations for the power line and channel parameters affected by time, location, frequency and a device connected to the power line.
In order to improve the reliability, in a method according to conventional technologies, a master device and a slave device for power line carrier are connected in parallel via an inductor or capacitor and coupled between a three-phase line and a zero line. In this method, three groups of coupling circuits or devices are needed, hence the installation is complicated and the cost is high.
In another method, carrier signals with different frequencies are respectively coupled to three phases to transmit data. Multiple carrier signals are modulated by multiple modulation circuits to generate balanced three-phase power line carrier signals including a first phase signal, a second phase signal and a third phase signal, and the balanced three-phase power line carrier signals are coupled into the three-phase line. In this method, multiple carrier modulation circuits and receiving devices are needed, hence the cost is also high.